Machines for molding closure shells, or molding sealing liners within closure shells, typically include a turret or carousel that rotates around a vertical axis. A plurality of molds are provided around the periphery of the carousel, in the form of male and female mold sections that are aligned along vertical axes parallel to the axis of rotation. Cams drive one or both of the mold sections of each pair between an open position, in which a molded part is stripped from the male mold section and a charge of plastic material is placed in the female mold section, and a closed position in which the male and female mold sections are brought together to compression mold the shell or liner. In a liner machine, premade shells are placed in a nest when the mold sections are open, and a charge or pellet of liner material is placed within the shell before the molds are closed. U.S. Patents that illustrate machines of this type for compression molding plastic closure shells include U.S. Pat. Nos. 5,670,100, 5,989,007, 6,074,583 and 6,478,568. U.S. Patents that illustrate machines of this type for compression molding sealing liners within closure shells include U.S. Pat. No. 5,451,360.
Although vertical axis carousel-type machines of the noted type have enjoyed substantial commercial acceptance and success, innovation remains desirable. In particular, in vertical axis carousel-type machines, the mold forces and the weight of the rotating equipment are parallel to the vertical axis of rotation, creating a bending moment with respect to the axis of rotation and the bearings and shaft that support the carousel. Carousel-type machines also require a substantial amount of valuable floor space in a manufacturing facility. It is a general object of the present disclosure, in accordance with one aspect of the disclosure, to provide a method and apparatus for compression molding plastic articles, such as plastic closures and plastic liners within closure shells, which reduce the forces applied to the support frame and bearings, reduce maintenance requirements and the amount of energy needed to operate the machine, and/or reduce the amount of floor space required per machine.
The present disclosure involves a number of aspects that can be implemented separately from or in combination with each other.
A mold core in accordance with one aspect of the present disclosure, which can be implemented for either compression and injection molding, includes a forming pin having a hollow interior and an end wall. A passage, preferably in the form of a hollow tube, extends into the hollow interior of the forming pin and has an end sealingly secured at a position spaced from the end wall of the forming pin. A poppet valve is disposed on the end wall of the forming pin. The poppet valve is operatively coupled to the forming pin and responsive to movement of the forming pin during operation to open the poppet valve and assist stripping of molded articles from the mold core. In the preferred embodiment, a spool valve feeds air under pressure through an air passage to open the poppet valve. The poppet valve includes a valve element having an outer end at the end face of the forming pin and an inner end adjacent to the end of the passage. A spring preferably biases the valve element to a closed position. The spring preferably comprises a coil spring captured in compression between the valve element and the forming pin.
A mold cavity in accordance with another aspect of the disclosure, for either compression or injection molding plastic articles, is adapted to be secured in a pocket on a molding machine having coolant feed and return passages opening into the pocket. The mold cavity includes a mold cavity seat adapted to be received in the pocket and a mold cavity insert secured within the seat. The seat and insert have opposed surfaces that form first coolant passages between the seat and the insert, and the seat has second coolant passages for connection to the feed and return passages in the machine for circulating coolant from the machine through the mold cavity and back to the machine. The second coolant passages in the cavity seat preferably are such that the mold cavity, including both the seat and the insert, are adapted to be rotated within the pocket selectively to open and close the first and second passages to coolant flow. The cavity preferably includes indicia for registry with indicia on the cavity support to indicate whether the first and second passages are open or closed to coolant circulation.
In accordance with a further aspect of the present disclosure, which can be implemented for either compression molding and injection molding, a mold element, such as a mold core and/or a mold cavity, has at least two components, at least one of which has at least one surface channel that, in assembly with another component, cooperates with an opposing surface of the other component to form a passage for circulating coolant between the components. The components preferably are secured to each other by e-beam welding, which localizes the heating to the mating surfaces and allows the assembled components to cool rapidly and retain their hardnesses. E-beam welding also reduces the likelihood of distortion of the mating components, and permits accurate control of the areas to be joined. E-beam welding does not require use of a separate joining material, but rather heat-fuses the components to each other.